The November 2002 eruption of Piton de la Fournais

Authors: Nathalie Vigouroux A E WilliamsJones Paul Wallace Thomas Staudacher

Publish Date: 2009/06/06

Volume: 71, Issue: 9, Pages: 1077-

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Abstract

The November 2002 eruption of Piton de la Fournaise in the Indian Ocean was typical of the activity of the volcano from 1999 to 2006 in terms of duration and volume of magma ejected The first magma erupted was a basaltic liquid with a small proportion of olivine phenocrysts Fo81 that contain small numbers of melt inclusions In subsequent flows olivine crystals were more abundant and richer in Mg Fo83–84 These crystals contain numerous melt and fluid inclusions healed fractures and dislocation features such as kink bands The major element composition of melt inclusions in this later olivine Fo83–84 is out of equilibrium with that of its host as a result of extensive postentrapment crystallization and Fe2+ loss by diffusion during cooling Melt inclusions in Fo81 olivine are also chemically out of equilibrium with their hosts but to a lesser degree Using olivine–melt geothermometry we determined that melt inclusions in Fo81 olivine were trapped at lower temperature 1182 ± 1°C than inclusions in Fo83–84 olivine 1199–1227°C This methodology was also used to estimate eruption temperatures The November 2002 melt inclusion compositions suggest that they were at temperatures between 1070°C and 1133°C immediately before eruption and quenching This relatively wide temperature range may reflect the fact that most of the melt inclusions were from olivine in lava samples and therefore likely underwent minor but variable amounts of posteruptive crystallization and Fe2+ loss by diffusion due to their relatively slow cooling on the surface In contrast melt inclusions in tephra samples from past major eruptions yielded a narrower range of higher eruption temperatures 1163–1181°C The melt inclusion data presented here and in earlier publications are consistent with a model of magma recharge from depth during major eruptions followed by storage cooling and crystallization at shallow levels prior to expulsion during events similar in magnitude to the relatively small November 2002 eruptionWe would like to thank Eric Delcher Université de la Réunion JeanLouis Cheminée Observatoire Volcanologique du Piton de la Fournaise and MarcAntoine Longpré McGill University for their help in the field and in sample collection Patrick Bachèlery Université de la Réunion provided important guidance and support We are very grateful to Jim Clark McGill University and John Donovan University of Oregon for performing the microprobe analyses Discussions with Don Baker and David Dolejs McGill University helped clarify issues of olivine crystallization Comments by Hélene Bureau and formal reviews by Keith Putirka Ivan Vlastélic and Peter Michael greatly improved the final manuscriptThe project was supported by a Natural Sciences and Engineering Research Council of Canada Undergraduate Student Research Award to NV and Discovery grant to AEWJ as well as travel funds provided by the Office FrancoQuébécois de la Jeunesse awarded to NV

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